JPH06317118A - Self-diagnostic device for variable valve timing control device - Google Patents

Abstract

PURPOSE:To conduct a diagnosis for troubles, including mechanical troubles in addition to electric troubles in a variable valve timing control device. CONSTITUTION:It is judged that the water temperature Tw, the number of revolutions Ne, and loads conform to specified diagnostic conditions, and a variable valve timing control solenoid 4 is in an OFF-state, and not in a highland travelling state. When these conditions are satisfied, the quantity QA of intake-air in the OFF-state of the solenoid 4 is sampled. Then, the solenoid 4 is forcedly turned ON, and the quantity QA1 of intake air is sampled under the condition. When the deviation DELTAQ between the air quantity QA1 and the air quantity QA is judged less then a specified, value, the system is judged to be in trouble.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a self-diagnosis device for a variable valve timing control device, and more particularly to a variable valve timing control device for variably controlling the valve timing of an internal combustion engine according to a control signal output according to engine operating conditions. The present invention relates to a technique for diagnosing a failure of a control device.

[0002]

2. Description of the Related Art Conventionally, a variable valve timing control device has been provided for operating a variable valve timing mechanism for switching the opening / closing timing of an intake valve of an engine in accordance with engine operating conditions. Increasing the amount of overlap in the open state of the valve to increase the filling efficiency by using the intake inertial force (edited by "New model car manual (FGY32-1)" published by Nissan Motor Co., Ltd. Date: August 1991 etc.).

In the variable valve timing control device as described above, the variable valve timing control solenoid is turned on / off by a control signal output from a control unit for inputting, for example, a rotation signal and an intake air amount signal.
By doing so, the hydraulic pressure for operating the variable valve timing mechanism is controlled to switch the opening / closing timing of the intake valve.

[0004]

By the way, as a method of diagnosing a failure of the variable valve timing control device as described above, it is determined whether or not a desired control signal is transmitted to the variable valve timing control solenoid. There was a method of confirming by taking a control signal into the control unit from a signal line near the variable valve timing control solenoid.

However, according to such a method, the variable valve timing control solenoid is actually turned on even though the ON control signal is output.
If the solenoid is operating normally without switching to the operating state suitable for N control, or the hydraulic circuit or valve timing variable mechanism is abnormal, the desired switching control is performed. It was not possible to diagnose a mechanical failure that does not exist, and in some cases, the valve timing was not switched to the desired state, but the valve timing was erroneously diagnosed as normal.

The present invention has been made in view of the above problems, and in a variable valve timing control device for an engine,
It is an object of the present invention to provide a self-diagnosis device capable of performing a diagnosis including mechanical failure and to improve the diagnosis performance.

[0007]

The present invention is a self-diagnosis device for a variable valve timing control device which variably controls the valve timing of an internal combustion engine based on a control signal output from a control unit according to engine operating conditions. And is configured as shown in FIG. In FIG. 1, the intake air amount detection means detects the intake air amount of the engine.

Further, the valve timing forced variable means is
The control signal is forcibly switched to forcibly change the valve timing for self-diagnosis. Then, the change amount of the intake air due to the switching of the valve timing by the air amount change calculating device and the valve timing forced changing device is calculated based on the detection value of the intake air amount detecting device.

The self-diagnosis means carries out a failure diagnosis of the variable valve timing control device based on the amount of change calculated by the air amount change calculation means.

[0010]

According to this structure, in the variable valve timing control device in which the valve timing is variably controlled based on the control signal output according to the engine operating condition, first, the valve timing is forcibly irrespective of the engine operating condition. It is required to determine how much the intake air amount detected by the intake air amount detecting means changes with the switching of the valve timing.

If the valve timing is switched normally, the intake air amount should change due to the change in the charging efficiency. If the intake air amount does not change even if the valve timing is changed, the valve is controlled by the control signal. It can be estimated that the valve timing is not actually switched even if the timing switching control is performed. Therefore,
When the change in the air amount due to the compulsory switching of the valve timing is small, it can be determined that the variable valve timing control device has some kind of failure including electrical failure and mechanical failure.

[0012]

EXAMPLES Examples of the present invention will be described below. FIG. 2 is a diagram showing a configuration example of a variable valve timing control device according to the present invention. An internal combustion engine to which the variable valve timing control device is applied includes an intake side camshaft and an exhaust side camshaft independently of each other. It is a thing.

The variable valve timing controller shown in FIG. 2 is attached to the intake cam sprocket 1 and has a variable valve timing mechanism 3 for variably controlling the phases of a crankshaft (not shown) and the intake camshaft 2. A variable valve timing control solenoid 4 that controls the supply of hydraulic pressure for operating the variable valve timing mechanism 3, and a control that outputs an on / off control signal to the variable valve timing control solenoid 4 according to the operating conditions of the engine. And the unit 5.

As shown in FIGS. 3 and 4, the variable valve timing control solenoid 4 has the rod when the solenoid provided on the base end side (upper side in FIGS. 3 and 4) is off (non-energized). 11 is retracted to the solenoid side, and when the solenoid is on (energized), the rod 11
Extends away from the solenoid. On the other hand, at the tip of the housing 12 supported so as to surround the rod 11, there is internally provided a cylindrical valve body 13 which is guided by the inner peripheral surface of the housing 12 and moves in the axial direction. The valve body 13 is biased toward the rod 11 side by a coil spring 14 which is interposed between the valve body 13 and the tip end portion of the housing 12, and the biasing force causes the valve body 13 to contact the tip end surface of the rod 11. As a result, the valve body 13 moves in the axial direction in conjunction with the forward / backward movement of the rod 11.

An inlet hole 15 is provided in the peripheral wall of the front end of the housing 12 for introducing hydraulic oil pressure-fed from an unillustrated hydraulic source into the space surrounded by the inner periphery of the housing 12 and the inside of the valve body 13. It is open. Further, the valve body 13 is provided with a communication hole 16 for discharging the hydraulic oil introduced through the introduction hole 15 into a space surrounded by the inner circumference of the housing 12 and the outer circumference of the rod 11 outside the valve body 13. . Further, a drain hole 17 facing a space surrounded by the inner circumference of the housing 12 and the outer circumference of the rod 11 is opened in the peripheral wall of the housing 12.

Here, when the variable valve timing control solenoid 4 is in the off (non-energized) state, the rod 11 retracts to the solenoid side, so that the valve body 13 is moved to the housing.
12 away from the tip, in this state the peripheral wall of the valve body 13 and the introduction hole 15 do not interfere, the hydraulic oil is introduced into the housing 12 against the introduction hole 15, through the communication hole 16 in the housing 12. And is discharged from the drain hole 17.

On the other hand, when the variable valve timing control solenoid 4 is in the ON (energized) state, the rod 11 moves to the valve body.
By extending to the 13 side, the valve body 13 descends toward the tip of the housing 12, and the peripheral wall of the valve body 13 closes the introduction hole 15 from the inside, so the hydraulic oil is discharged through the drain hole 17. It will not be done. The hydraulic oil passage 18 communicating with the introduction hole 15 communicates with the hydraulic oil passage of the variable valve timing mechanism 3 on the upstream side thereof, and when the solenoid 4 is off, the hydraulic oil is discharged through the drain hole 17. As a result, the hydraulic pressure does not act on the variable valve timing mechanism 3, and when the solenoid 4 is turned on and the drain hole 17 is closed, the hydraulic pressure acts on the variable valve timing mechanism 3.

The hydraulic oil passage 18 communicates with a hydraulic oil passage 19 provided in the camshaft 2 before reaching the solenoid 4, and the hydraulic oil is not discharged from the solenoid 4 side when the solenoid 4 is on. Then, the hydraulic oil passage 19
The hydraulic oil supplied to the cam sprocket 1 reaches the front surface of the plunger 21 built in the cam sprocket 1 via the hydraulic oil passage 20 provided in the cam sprocket 1. And plunger 21
The hydraulic oil that has reached the front surface of the cylinder acts to press the plunger 21 against the camshaft 2 side due to the hydraulic pressure.

Since the plunger 21 meshes with the cam sprocket 1 and the cam shaft 2 by the helical gear 22, when it is pressed by the hydraulic pressure, it moves axially to the stopper position while rotating, and at this time, the cam sprocket 1 Since it is fixed by a timing chain (not shown), the camshaft 2 side is the plunger.
It rotates with 21 and cam sprocket 1 and cam shaft 2
The relative position in the circumferential direction with changes.

On the other hand, when the control solenoid 4 is turned off, the hydraulic oil is discharged through the drain hole 17 of the solenoid 4, so that the force for pressing the plunger 21 against the camshaft 2 side is lost, and the plunger is removed. 21 is returned to the original position separated from the side of the camshaft 2 by the urging force of the return spring 23. In this way, in the variable valve timing control device of the present embodiment, the phase of the intake side camshaft 2 is changed with respect to the crankshaft to change the phase of the intake side cam with the operating angle kept constant. In the embodiment, FIG.
As shown in (a) and (b), the opening timing of the intake valve is delayed when the solenoid 4 is off, and conversely, the opening timing of the intake valve is early when the solenoid 4 is on and the amount of overlap with the exhaust valve is large. Is increasing.

Turning on / off of the solenoid 4 is controlled by a control signal from the control unit 5, and the solenoid 4 is turned on / off according to engine operating conditions.
The control unit 5 includes a crank angle sensor 8, an air flow meter 9 (intake air amount detecting means), in order to turn off the intake valve and change the opening / closing timing of the intake valve in conformity with operating conditions.
The engine rotation signal Ne, the engine intake air amount signal Q, and the cooling water temperature signal Tw from the water temperature sensor 10 are input.

Then, the control unit 5 incorporating the microcomputer has the intake air amount signal Q and the rotation signal N.
The engine load equivalent value is calculated from e and the on / off state of the solenoid 4 is determined by referring to the valve timing control map (see FIG. 6) set in advance with the engine load and rotation as parameters, and the determination is performed. An on / off control signal corresponding to the above is output to the solenoid 4.

Further, in the present embodiment, the control unit 5 is provided with the function of performing self-diagnosis of the variable valve timing control device having the above-mentioned configuration. The state of self-diagnosis in the control unit 5 will be described below with reference to the flowchart of FIG. In the present embodiment, the control unit 5 is provided with the functions of the valve timing forced changing means, the air amount change calculating means, and the self-diagnosis means by software as shown in the flow chart of FIG.

In the flowchart of FIG. 7, step 1 (denoted as S1 in the figure. The same applies hereinafter) to step 5
Then, it is determined whether or not various conditions for self-diagnosis are satisfied. First, in step 1, it is determined whether or not the cooling water temperature Tw is equal to or higher than a predetermined temperature (for example, 60 ° C.).

When the cooling water temperature Tw is equal to or higher than the predetermined temperature, the routine proceeds to the next step 2, where the engine speed Ne is
Is within a predetermined speed range (for example, a low rotation range of about 1500 to 2000 rpm). When the rotation speed Ne is within the predetermined speed range, the routine further proceeds to step 3, where it is determined whether the engine load is within the predetermined low load region.
The representative value of the engine load is obtained from the intake air amount Q and the engine rotation speed Ne.

When it is determined by the above determination that the cooling water temperature Tw is equal to or higher than the predetermined temperature, the engine rotation speed Ne is within the predetermined speed range, and the engine load is within the predetermined range, the valve timing is forcibly changed. However, it is presumed that the exhaust property is not greatly affected, and the process proceeds to the next step 4. In this embodiment, as will be described later, the valve timing is forcibly switched for self-diagnosis, and the diagnosis is performed based on the change in the intake air amount generated at that time. We want to avoid the deterioration of exhaust quality and the sudden change in drivability that accompany the switching of valve timing.
Whether or not the operating conditions are met is determined in steps 1 to 3.

When it is determined in step 1 to step 3 that the operating condition is such that even if the forced valve timing switching control is performed, the operation proceeds to step 4 and the variable valve timing control solenoid 4 is turned off.
It is determined whether or not the control signal is output, in other words, the valve timing is controlled such that the overlap amount is small.

When it is determined in step 4 that the control signal is in the off state, the process proceeds to step 5 and it is determined whether or not the vehicle is traveling in high altitude. Such highland determination can be performed based on, for example, a detected value of atmospheric pressure, but various known methods can be used. In high altitude running conditions, the change in intake air amount due to switching of valve timing is less than in low altitude conditions, making it impossible to secure diagnostic accuracy. Therefore, it is not in high altitude running conditions (altitude below a certain level). Under the condition, the procedure proceeds to the diagnostic step after step 6.

In step 6, the intake air amount Q detected by the air flow meter 9 is set to QA as the air amount corresponding to the OFF control state of the variable valve timing control solenoid 4. In step 7, the solenoid 4 should be turned off from the operating condition, but the solenoid 4 is forced to turn off for self-diagnosis.
The N control signal is output to forcibly control the valve timing in the direction in which the overlap amount increases (see FIG. 5B).

Then, in the next step 8, the intake air amount Q detected by the air flow meter 9 is sampled immediately after the solenoid 4 is forcibly turned on as described above,
This is QA1 as the air amount corresponding to the control signal ON state.
Set to. Even if the ON control signal is output to the solenoid 4, the valve timing is not switched instantaneously, and a time lag is caused by a delay in hydraulic control. Therefore, the air flow at the time when the delay time has passed from the OFF to ON switching. It is advisable to sample the meter detection value.

In step 9, the air amount QA1 in the ON control state of the solenoid 4 obtained as described above is obtained.
And the deviation ΔQ (←
QA1-QA) is calculated. That is, the deviation ΔQ is data indicating a change in the air amount due to the valve timing being switched by forcibly switching the solenoid 4 from OFF to ON.

When the deviation ΔQ is calculated, the next step
At 10, the deviation ΔQ is compared with a predetermined value to determine whether or not the deviation ΔQ is an amount commensurate with the switching of the valve timing. In this embodiment, FIG.
As shown in, the solenoid 4 is turned on in the low / medium speed, low load range.
In the FF, the overlap amount is reduced in this region to improve the exhaust property rather than the intake efficiency, and the compulsory ON control in step 7 is performed in this region.

Therefore, the forced solenoid 4 is turned on.
The control improves the intake efficiency by advancing the closing timing of the intake valve, and the intake air amount Q increases as the intake efficiency increases.
Should show an increase change above a predetermined level. However, when there is a failure such that the valve timing does not actually switch according to the control signal output to the solenoid 4, the intake efficiency does not change, so even if the control signal is switched, the intake air amount is changed. No change will occur.

Therefore, if it is determined in step 10 that the deviation ΔQ is less than or equal to the predetermined value, it can be estimated that the valve timing is not actually switched according to the control signal, and conversely, the desired air When the amount change is obtained, it can be estimated that the valve timing is normally switched according to the control signal output to the solenoid 4.

If it is determined that the deviation ΔQ is greater than or equal to the predetermined value, the process proceeds to step 11 to determine whether the system is normal, and the control signal output to the solenoid 4 is determined according to the original operating conditions. The routine is terminated by returning to the OFF state. On the other hand, if it is determined that the deviation ΔQ is less than or equal to the predetermined value, it is presumed that some kind of failure has occurred, but instead of immediately making a failure determination, the routine proceeds to step 12, where the solenoid 4 Forced ON / OFF
It is determined whether the self-diagnosis by control is performed twice, and 1
If the failure is determined by the diagnosis only once, the process returns to step 7 to check again, and the diagnosis is performed again.

When it is determined that the deviation ΔQ is less than a predetermined value and there is a failure in the second time, the deviation ΔQ
Considering that the diagnostic result based on Q is reliable, the process proceeds to step 13 to judge the system failure. In the above embodiment, the opening / closing timing of the intake valve is variable while the operating angle is constant, but a variable valve timing control device having a configuration that changes the operating angle (lift amount) with the opening / closing timing may be used. Even when the valve timing is changed while the operating angle is constant, it is obvious that the variable mechanism is not limited to the above-mentioned variable mechanism.

Further, in the above embodiment, the O of the solenoid 4 is
Under the FF condition, the solenoid 4 is forcibly turned on,
I tried to find the change in the air amount at this time, but conversely,
The solenoid 4 is forcibly forced when the solenoid 4 is on.
May be turned off. However, in general, if the control for forcibly delaying the closing timing of the intake valve 4 is performed while advancing the closing timing of the intake valve by turning on the solenoid 4, it is thought that the drivability is greatly affected. Since it is predicted, the configuration in which the solenoid 4 is forcibly turned on under the OFF condition as in the above embodiment is preferable.

[0038]

As described above, according to the present invention, in the variable valve timing control device for variably controlling the valve timing of the internal combustion engine based on the control signal output from the control unit according to the engine operating condition, the valve timing The fact that the valve timing is actually switched according to the control signal is diagnosed by utilizing the fact that the intake air amount changes according to the forced switching of the control signal output system. In addition to the physical failure, mechanical failure of the valve timing control mechanism can be diagnosed, and it is possible to provide a highly reliable diagnosis result.

[Brief description of drawings]

FIG. 1 is a block diagram showing the basic configuration of the present invention.

FIG. 2 is a system schematic diagram showing an embodiment of the present invention.

FIG. 3 is a diagram showing a state of hydraulic control when a control signal is on.

FIG. 4 is a diagram showing a state of hydraulic control in the off state of a control signal.

FIG. 5 is a diagram showing a change in opening / closing timing of an intake valve due to ON / OFF of a control signal.

FIG. 6 is a diagram showing an on / off control region of a control signal.

FIG. 7 is a flowchart showing self-diagnosis control of the embodiment.

[Explanation of symbols]

 1 cam sprocket 2 cam shaft 3 variable valve timing mechanism 4 variable valve timing control solenoid 5 control unit 8 crank angle sensor 9 air flow meter 10 water temperature sensor 18-20 hydraulic fluid passage 21 plunger 22 helical gear 23 return spring

Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location G01M 15/00 Z 7324-2G

Claims (1)

[Claims] 1. A self-diagnosis device for a variable valve timing control device, which variably controls valve timing of an internal combustion engine based on a control signal output from a control unit according to engine operating conditions, the intake air amount of the engine being determined. Intake air amount detecting means for detecting, valve timing forced variable means for forcibly changing the valve timing for self-diagnosis by forcibly switching the control signal, and switching of valve timing by the valve timing forced variable means An air amount change calculating means for calculating the change amount of the intake air based on the detection value of the intake air amount detecting means, and a failure of the variable valve timing control device based on the change amount calculated by the air amount change calculating means. A variable valve timing control device comprising: self-diagnosis means for making a diagnosis; Self-diagnosis system.